When the CAYW picker is triggered, it should be shown.

According to https://stackoverflow.com/a/38801936/873282, setAlwaysOnTop(true) is the only way. true and then false did not have any effect here: https://stackoverflow.com/a/48798192/873282

Steps to test

Trigger CAYW - e.g., by cayw.http and executing the first GET

Mandatory checks

• I own the copyright of the code submitted and I license it under the MIT license
• [/] Change in CHANGELOG.md described in a way that is understandable for the average user (if change is visible to the user)
• [/] Tests created for changes (if applicable)
• [/] Manually tested changed features in running JabRef (always required)
• [/] Screenshots added in PR description (if change is visible to the user)
• [/] Checked developer's documentation: Is the information available and up to date? If not, I outlined it in this pull request.
• [/] Checked documentation: Is the information available and up to date? If not, I created an issue at https://github.com/JabRef/user-documentation/issues or, even better, I submitted a pull request to the documentation repository.